• Journal of the Korea Concrete Institute
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• v.27 no.4
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• pp.419-426
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• 2015

The purpose of this study is to investigate experimentally the optimum mix design and site application case of soil mixing wall (SMW) method which is cost-effective technique for construction of walls for cutoff wall and excavation support as well as for ground improvement before constructing LNG storage tank typed under-ground. Considering native soil condition in site, main materials are selected ordinary portland cement, bentonite as a binder slurry and also it is applied $1,833kg/m^3$ as an unit volume weight of native soil, Variations for soil mixing wall are as followings ; (1) water-cement ratio 4cases (2) mixing velocity (rpm) 3levels (3) bleeding capacity and ratio, compressive strength in laboratory and site application test. As test results, bleeding capacity and ratio are decreased in case of decreasing water-cement ratio and increasing mixing velocity. Required compressive strength (1.5 MPa) considering safety factors in site is satisfied with the range of water-cement ratio 150% below, and test results of core strength are higher than those of specimen strength in the range of 8~23% by actual application of element members including outside and inside in site construction work. Therefore, optimum mix design of soil mixing wall is proposed in the range of unit cement $280kg/m^3$, unit bentonite $10kg/m^3$, water-cement ratio 150% and mixing velocity 90rpm and test results of site application case are satisfied with the required properties.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.9
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• pp.658-665
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• 2009

Lean premixed combustors are used for significant NOx reduction which one of issues in current gas turbine combustor. This study was investigated to estimate the effects of the unmixedness of fuel-air, equivalence ratio on the instability mechanism, NOx emission and combustion oscillation in a lean premixed combustor. The experiments were conducted in a dump combustor at atmospheric pressure conditions using methane as fuel. The swirler angle was $45^{\circ}$, the degrees of fuel-air mixing were 0, 50 and 100 and inlet temperature was 650K. The equivalence ratio was ranging from 0.5 to 0.8. This paper shows that NOx emission was increased when the degree of fuel-air mixing is increased in same equivalence ratio and when equivalence ratio is increased. And the range of the combustion instability was enlarged as a function of increasing of the degree of fuel-air mixing.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.281-284
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• 2008

The flow of combustor in scramjet engine is supersonic speed. So residence time and mixing ratio are very important factors for efficient combustion. This study used open cavity on fuel/air mixing model and laser schlieren was carried out to investigate flow characteristics around a jet orifice and a cavity. A source of illumination has 10 ns endurance time so it can observe unsteady flow characteristics efficiently. Pressure was measured by varying momentum flux ratio. And the change of critical ignition point was observed to change of momentum flux ratio.

• Tribology and Lubricants
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• v.31 no.3
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• pp.102-108
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• 2015

In this research, we experimentally investigated the sealing performance of elastomeric rotary lip seals for washing machines. In general, NBR is used as a material for elastomeric rotary lip seals in washing machines, but the mixing formula of the rubber material can affect the sealing performance. In this study, we manufactured rotary lip seals using three kinds of NBRs with a different mixing formula, and examined the sealing performance using an acceleration test mode. The results of an SEM investigation into the surfaces of three kinds of specimens showed a much smaller wear volume and better sealing performance for the specimens with smaller particle sizes of mixing composition than for the specimen with the larger. Repeated deformation and recovery by the shaft-to-seal eccentricity on rotation were shown to cause a phase difference in the rubber material, and we measured the recovery ratio to find the influence of this phase difference on the sealing performance. As another method for checking the phase difference, we also measured tan ä, and a lower tan ä was revealed as the recovery ratio increased for each specimen. Specimens with a higher recovery ratio (lower tan ä) were shown to have a better sealing performance. Consequently, specimens with a smaller particle size in the mixing composition had a better sealing performance because they show a higher recovery ratio.

• Journal of Welding and Joining
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• v.23 no.3
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• pp.54-60
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• 2005

Tungsten Inert Gas(TIG) welding is today one of the most popular arc welding process because of its high quality welds and low equipment costs. Even if welding productivity increases with welding speed and current, this strategy is limited by the appearance of defects such as undercut and humping bead due to the depressed molten metal. The purpose of this study investigates the effect of He mixing ratio on the characteristics with high current and speed in TIG welding. The conclusions obtained permit to explain the arc start characteristics quantitatively and the maximum welding speed on stable bead formation with He mixing ratio for high current and speed TIG welding observed in experiments. Also through the relation of the maximum arc pressure and surface depression depth at high current and speed TIG welding, it made clear the mechanism of unstable bead formation.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.9-15
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• 2009

The flow of combustor in scramjet engine has supersonic speed so that the residence time and mixing ratio are very important factors for the efficient combustion. This study used open cavity(L/D=4.8) as a fuel/air mixing model. Laser schlieren visualization and pressure measurement were carried out to observe the flow characteristics around a jet orifice and a cavity at the time of fuel injection. As a result of 10ns laser schlieren, unsteady flow which was around the cavity could be observed effectively. Pressure was measured that momentum flux ratio(J) was changed. And the change of critical ignition point could be observed by the momentum flux ratio changed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.61-64
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• 2009

This study is reviewed fire resistance characteristics of high strength concrete according to changes in PP fiber mixing ratio and type of fine aggregate, and the results can be summarized as follows. As fire resistance characteristics, all plain crushed sands prevented spalling regardless of increase in mixing ratio of PP fiber. Mixtures other than the plain showed satisfactory spalling prevention when 0.05 % or more of PP fiber was mixed. After the fire resistance experiment, the plain showed 5.5 % of mass loss rate when fiber was not mixed and others could not be measured. According to increase in mixing ratio of fiber, river sand with fineness modulus of 2.2 showed most satisfactory result of 34 %${\sim}$42 %. Mass loss rate after fire resistance experiment was most satisfactory at about 10 % in the plain crushed sand without mixing of fiber, and all other mixes with 0.05 % PP fiber or more showed 5${\sim}$10 % loss rate.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.105-110
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• 2011

Recently, a deep mixture method as a soil improvement method of marine soft ground, which causes less noise and vibration than other methods, are widely used. In this study, for DCM(Deep Cement Mixing) method, one of the deep mixture method, optimum mixing ratio of clay-cement was suggested using uniaxial compression tests on specimens with various mixing ratio of claycement. In addition, the stability of a caisson on tangent circle-type and wall-type DCM treated ground was evaluated using centrifuge tests. As a result, optimum mixing ratio of clay-cement was 28.5% and the stability of the caisson on DCM treated ground was confirmed. However, the lateral displacement of the caisson on the wall-type DCM treated ground was 7% less and the settlement of that was 39% less than the case of the tangent-circle-type DCM method.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.44-50
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• 1999

For the prediction of combustion performance of the Unlike Impinging Quadlet Injector (OOOF type), mixing efficiency, mixing characteristic velocity, and efficiency of mixing characteristic velocity were obtained from the cold test. Water/kerosene were used for simulants, The momentum ratio of oxidizer and fuel were mixing correlating parameter. Orifice discharge coefficient, spray pattern and mass distribution were measured. As a result, invasion-depth had strong effect on mixing efficiency, mixing characteristic velocity, and efficiency of mixing characteristic velocity. Mixing efficiency and efficiency of mixing characteristic velocity showed maximum value for momentum ratio 1.67(TMR = 2.5), and fuel rich state showed larger decreasing ratio than oxidizer rich state.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.37-50
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• 2016

Gravel compaction pile (GCP) is widely used as it increases the bearing capacity of soft ground and reduces the consolidation settlement. Stress concentration ratio for GCP design is dependent on the area replacement, surcharge pressure and depth. However, a range of stress concentration ratio obtained through field, laboratory experiments and numerical analysis is large. Little study has been done on the stress concentration ratio for the mixing ratio of gravel and sand. The main objective of the study is to evaluate the stress concentration ratio for both area replacement ratio and mixing ratio through literature review and numerical analysis. Numerical analysis using the finite element program ABAQUS 6.12-4 has been performed for the composite ground with GCP. The excess pore water pressure and stress concentration ratio of composite ground have been analyzed for both the area replacement ratio and the mixing ratio. Based on the previous research results, a range of stress concentration ratio obtained from the field tests, laboratory tests, numerical analysis on the GCP studies is found to be 1.7-3.2, 2.0-7.5 and 2.0-6.5, respectively. Based on the numerical analysis results, as the area replacement ratio increases, the stress concentration ratio increases up to 30% and then decreases at 40%. Also, the stress concentration ratio tends to increase up to 70:30 and then to decrease after 60:40.